As is known in the art, plasticizing and/or softening additives are employed for a variety of reasons. Among these are facilitation of processing, and increasing flexibility and toughness of the polymer. In addition, there are cost advantages resulting from the substitution of a less expensive plasticizer in a formulation for a more expensive monomer or for another more expensive plasticizer.
Among the more important plasticizing additives are nonvolatile organic liquids and low-melting solids, for example, phthalate, adipate and sebacate esters, polyols such as ethylene glycol and its derivatives, tricresyl phosphate, castor oil, and the like.
Dibutyl phthalate (DBP) is a common plasticizing additive of choice for nitrocellulose lacquers, elastomers, and such thermosets as polyurethanes and epoxies. In use, for example, with epoxy resins, DBP may be used as a plasticizing additive with loading levels up to about 10 percent by weight (wt %) at which level desirable properties begin to be adversely affected. Analogs of the phthalate such as the dioctyl compound (DOP) are often similarly employed. The phthalates are oxygenated hydrocarbons.
Other plasticizing/softening additives for elastomers, epoxies and polyurethanes include styrenated tetralins such as ACTREL 400. Of course, styrene is an arene, but tetralin, i.e., tetrahydronaphthalene, is a bicyclic alkane.
Certain alkylbiphenyls have been generally mentioned as plasticizing/softening additives for certain polymer systems. For example, in U.S. Pat. No. 2,449,928, it is disclosed that certain binuclear aromatic compounds, which generally include alkyl- and alkenyl-substituted analogs, for example, phenyl styrene, i.e., 2-ethenylbiphenyl, can be employed to plasticize elastomers such as synthetic rubbers and rubber-like plastics to include elastolenes such as butadiene polymers and copolymers, particularly copolymerized with acrylic nitrile. In U.S. Pat. No. 2,786,040, it is disclosed that alkylated biphenyls such as isopropylbiphenyl and diisopropylbiphenyl can be employed to plasticize polystyrene-type water-base emulsion paints.
Other plasticizing/softening additive modifications are known. For example, in U.S. Pat. No. 2,897,230, it is disclosed that certain aromatic precursors could be condensed with a fumaric acid to provide oxygenated adducts particularly useful to plasticize polyvinyl chloride (PVC) and certain copolymers of PVC. In U.S. Pat. No. 2,945,832, it is disclosed that a plastisol coating such as made from PVC liquid dispersions could be improved, for example, to make them thinner by employment of a combination of ester plasticizing additives, e.g., DOP, with an alkylbiphenyl, e.g., isopropylbiphenyl, or butyl fumarate with diisopropylbiphenyl.